Javascript 将6位颜色代码转换为3位

如果可能的话，我想把给定的十六进制颜色转换成3位数。例如：

#ffffff - #fff
#001122 - #012
#012345 - #012345

var hex = "#aabb00";
if ((hex.charAt(1) == hex.charAt(2))
  && (hex.charAt(3) == hex.charAt(4))
  && (hex.charAt(5) == hex.charAt(6))) {
    hex = "#" + hex.charAt(1) + hex.charAt(3) + hex.charAt(5);
}

有人知道怎么做吗

我在谷歌网站上找到了这个正则表达式，但我不知道如何使用它们：/

# shorten your CSS
sed -re 's/#(([0-9a-fA-F])\2)(([0-9a-fA-F])\4)(([0-9a-fA-F])\6)/#\2\4\6/'

# expand: the three-digit RGB notation (#rgb) is converted into six-digit form (#rrggbb) by replicating digits
sed -re 's/#([0-9a-fA-F])([0-9a-fA-F])([0-9a-fA-F])\b/#\1\1\2\2\3\3/'

# works in egrep too
grep -E '(([0-9a-fA-F])\2)(([0-9a-fA-F])\4)(([0-9a-fA-F])\6)'

---

可能下面的代码将帮助您：

function hexToRgb(hex) {
    // Expand shorthand form (e.g. "03F") to full form (e.g. "0033FF")
    var shorthandRegex = /^#?([a-f\d])([a-f\d])([a-f\d])$/i;
    hex = hex.replace(shorthandRegex, function(m, r, g, b) {
        return r + r + g + g + b + b;
    });

    var result = /^#?([a-f\d]{2})([a-f\d]{2})([a-f\d]{2})$/i.exec(hex);
    return result ? {
        r: parseInt(result[1], 16),
        g: parseInt(result[2], 16),
        b: parseInt(result[3], 16)
    } : null;
}

function rgbToShortHex(rgb){
    var hexR = Math.round(rgb.r / 17).toString(16);
    var hexG = Math.round(rgb.g / 17).toString(16);
    var hexB = Math.round(rgb.b / 17).toString(16);
    return "#"+hexR+""+hexG+""+hexB;
}

function getShortHexColorCode(code){
    var rgb = hexToRgb(code);
    return rgbToShortHex(rgb);
}
alert(getShortHexColorCode("#ffffff"));

---

检查小提琴

可能在下面代码将帮助您：

function hexToRgb(hex) {
    // Expand shorthand form (e.g. "03F") to full form (e.g. "0033FF")
    var shorthandRegex = /^#?([a-f\d])([a-f\d])([a-f\d])$/i;
    hex = hex.replace(shorthandRegex, function(m, r, g, b) {
        return r + r + g + g + b + b;
    });

    var result = /^#?([a-f\d]{2})([a-f\d]{2})([a-f\d]{2})$/i.exec(hex);
    return result ? {
        r: parseInt(result[1], 16),
        g: parseInt(result[2], 16),
        b: parseInt(result[3], 16)
    } : null;
}

function rgbToShortHex(rgb){
    var hexR = Math.round(rgb.r / 17).toString(16);
    var hexG = Math.round(rgb.g / 17).toString(16);
    var hexB = Math.round(rgb.b / 17).toString(16);
    return "#"+hexR+""+hexG+""+hexB;
}

function getShortHexColorCode(code){
    var rgb = hexToRgb(code);
    return rgbToShortHex(rgb);
}
alert(getShortHexColorCode("#ffffff"));

---

检查fiddle

可能有一种更短更甜的方法，但您可以在十六进制颜色的字符之间执行简单的字符比较，如有必要，还可以手动组装字符串，例如：

#ffffff - #fff
#001122 - #012
#012345 - #012345

var hex = "#aabb00";
if ((hex.charAt(1) == hex.charAt(2))
  && (hex.charAt(3) == hex.charAt(4))
  && (hex.charAt(5) == hex.charAt(6))) {
    hex = "#" + hex.charAt(1) + hex.charAt(3) + hex.charAt(5);
}

---

可能有一种更短更甜的方法，但您可以在十六进制颜色的字符之间执行简单的字符比较，如有必要，还可以手动组装字符串，例如：

#ffffff - #fff
#001122 - #012
#012345 - #012345

var hex = "#aabb00";
if ((hex.charAt(1) == hex.charAt(2))
  && (hex.charAt(3) == hex.charAt(4))
  && (hex.charAt(5) == hex.charAt(6))) {
    hex = "#" + hex.charAt(1) + hex.charAt(3) + hex.charAt(5);
}

---

只需进行串联，var color='#001122'；输出=

${color[1]+color[3]+color[5]}

；-）只需进行串联，var color='#001122'；输出=

${color[1]+color[3]+color[5]}

；-）